Recently there have been a few changes to the toolserver, including IPv6.
Around the same time, ACC (enwp Account Creation Project) stopped recording
request IPs and replacing them with wikimedia IPs. Examples
are 91.198.174.197 and 91.198.174.208. Could it be anything from the
toolserver side? I don't think we have had any changes made to the ACC code
in the past few days (Though stwalkerster might have updated the stuff from
the sandbox to live--though we haven't had any changes in the IP section
anyways).
-ManishEarth